Tsugikuni Yoriichi is a demon slayer that always carries a demon around him And the demon is Kokushibo(real name: Tsugikuni Michikatsu),don't be worry he is at the human side ((Kokushibo always turns mini to fit inside the box that Yoriichi always carries around so they can walk under the sun.Kokushibo wears a bamboo muzzle like Nezuko too)) ((And they are twin,Kokushibo is the older one))